Wireless devices and systems including examples of cross correlating wireless transmissions

ABSTRACT

Examples described herein include systems and methods which include wireless devices and systems with examples of cross correlation including symbols indicative of radio frequency (RF) energy. An electronic device including a statistic calculator may be configured to calculate a statistic including the cross-correlation of the symbols. The electronic device may include a comparator configured to provide a signal indicative of a presence or absence of a wireless communication signal in the particular portion of the wireless spectrum based on a comparison of the statistic with a threshold. A decoder/precoder may be configured to receive the signal indicative of the presence or absence of the wireless communication signal and to decode the symbols responsive to a signal indicative of the presence of the wireless communication signal. Examples of systems and methods described herein may facilitate the processing of data for wireless communications in a power-efficient and time-efficient manner.

CROSS REFERENCE TO RELATED APPLICATION(S

This application is a continuation of pending U.S. Pat. Application No.17/090,123 filed Nov. 5, 2020, which application is a continuation ofU.S. Pat. Application No. 16/426,518 filed May 30, 2019 and issued asU.S. Pat. No. 10,841,076 on Nov. 17, 2020, which is a continuation ofU.S. Pat. Application No. 15/374,831 filed Dec. 9, 2016 and issued asU.S. Pat. No. 10,333,693 on Jun. 25, 2019. The aforementionedapplications, and issued patents, are incorporated herein by reference,in their entirety, for any purpose.

BACKGROUND

There is interest in moving wireless communications to “fifthgeneration” (5G) systems. 5G promises increased speed and ubiquity, butmethodologies for processing 5G wireless communications have not yetbeen set. Implementing 5G systems may require more efficient use of thewireless spectra.

Example 5G systems may be implemented using multiple-inputmultiple-output (MIMO) techniques, including “massive MIMO” techniques,in which multiple antennas (more than a certain number, such as 8 in thecase of example MIMO systems) are utilized for transmission and/orreceipt of wireless communication signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a system arranged in accordancewith examples described herein.

FIG. 2 is a schematic illustration of an example communication detectorarranged in accordance with examples described herein.

FIG. 3 is a schematic illustration of an electronic device arranged inaccordance with examples described herein.

FIG. 4 is a schematic illustration of a method arranged in accordancewith examples described herein

DETAILED DESCRIPTION

Certain details are set forth below to provide a sufficientunderstanding of embodiments of the invention. However, it will be clearto one skilled in the art that embodiments of the invention may bepracticed without various of these particular details. In someinstances, well-known wireless communication components, circuits,control signals, timing protocols, computing system components, andsoftware operations have not been shown in detail in order to avoidunnecessarily obscuring the described embodiments of the invention.

By using information from massive multi-inputs and multi-outputs (MIMO)systems described herein (which may be utilized in 5G wireless systems),examples described herein detect unused frequency bands (e.g. frequencybands which are idle and/or available for use). The unused frequencybands may have been licensed to other communications and broadcastingsystems in some examples. Examples described herein may utilize anautocorrelation between different MIMO transmission channels incombination with a cross-correlation between those MIMO transmissionchannels (or different transmission channels) to determine whether aparticular frequency or frequency band is idle and/or available for use.

5G systems may advantageously make improved usage of frequency spectrumresources. Frequency bands in some systems may be assigned by regulatoryauthorities such as the Federal Communication Commission (FCC).Assignments may be made, for example, according to differentapplications such as digital broadcasting and wireless communication.These licensed and assigned frequencies may be idled and wasted if thereis neither service nor transmission, which may often be the case in manyapplications. Such idling may not be acceptable when improved efficiencyis demanded from the wireless spectrum. Moreover, with the fastdevelopment of digital transmission and communications, there are fewerand fewer unlicensed frequency bands and it may be advantageous tore-use those licensed frequency bands if they are idle. For example, theFCC has officially proposed to open some UHF bands for unlicensed usesand is also considering how to use the frequency bands which are over 6GHz (e.g. millimeter wave bands). Examples described herein may beutilized to detect unused bands (e.g. frequency bands which are idleand/or available for use). Without a good detection scheme,transmissions made in the band may be subject to strong interference byother transmissions occurring in the same band.

In some examples, it may be advantageous to provide an electronic devicethat may only decode wireless communications when signals are detectedat the transceiver. Such an approach may conserve power consumed by theelectronic device, for example, for decoding of wireless communications.In some examples, the detector and/or decoder portion of the electronicdevice may be powered off until an indication is provided to thatdetector and/or decoder that a signal is present in a particular portionof the wireless spectrum. The indication may indicate that receivedsignals at the multiple antennas of the electronic device include atarget signal (e.g. a 5G wireless communication signal). Utilizing suchan approach, the detector and/or decoder portion of the electronicdevice may not process noise signals that may be received at theantennas. In contrast, a conventional MIMO transceiver may process anddecode such noise signals, only being realized as noise once thedetector and/or decoder portion of the MIMO transceiver has processedthe received signals.

Examples described herein include systems and methods which includewireless devices and systems with communication detectors which mayutilize a cross-correlation between multiple wireless channels togenerate a statistic. Such a statistic may be compared to a threshold todetermine whether a communication signal is present or if the portion ofthe spectrum is idle and/or available for use. In some examples, acommunication detector may be included in an electronic device thatincludes multiple antennas. Radio frequency (RF) energy may be incidenton multiple antennas (e.g. a first and second antenna). Thecommunication detector may perform a cross-correlation between symbolsindicative of the RF energy received on the first and second antennas ina portion of the wireless spectrum (e.g. at a particular frequencyand/or frequency band) and compare the cross-correlation to a thresholdto determine whether a wireless communication is present in that portionof the wireless spectrum. The RF energy received on the first and secondantenna in a portion of the wireless spectrum may be referred to as RFsignals from each antenna. The communication detector may provide asignal indicative of either (1) a wireless communication signal beingpresent in the portion of the wireless spectrum (e.g. a ‘1’); or (2) theportion of the wireless spectrum being idle and/or available for use(e.g. a ‘0’). Receivers, transmitters, and/or transceivers describedherein may receive the incident RF energy response to the indicationthat the wireless communication is present in the portion of thewireless spectrum, and generate symbols that are cross correlated thecommunication detector. A decoder/precoder of the electronic devicedescribed herein may receive a signal indication from the communicationdetector and may transmit and/or encode in the portion of the wirelessspectrum indicated as being idle and/or available for use. Generally, aportion of the wireless spectrum may be considered idle and/or availablefor use herein when the statistic calculated by a communication detectorusing a cross-correlation between wireless channels is below athreshold. The threshold may be set, for example, such that when thecross-correlation between wireless channels is below the threshold, acommunication may be sent on the channel(s) with an acceptable amount ofinterference.

FIG. 1 is a schematic illustration of a system arranged in accordancewith examples described herein. System 100 includes electronic device102, electronic device 104, antenna 106, antenna 108, antenna 110,antenna 112, antenna 114, antenna 116, communication detector 118,transceiver 120, transceiver 124, transceiver 128, communicationdetector 122, transceiver 124, transceiver 126, transceiver 130,transceiver 132. The electronic device 102 may include antenna 106,antenna 108, and antenna 110. The electronic device 102 may includecommunication detector 118, transceiver 120, transceiver 124, andtransceiver 128. Communication detector 118 and transceivers 120, 124,128 may be in communication with one another. Each transceiver 120, 124,128 may in communication with a respective antenna, such as antenna 106,antenna 108, and antenna 110. The electronic device 104 may includeantenna 112, antenna 114, and antenna 116. The electronic device 104 mayinclude communication detector 122 and transceivers 124, 126, 132.Communication detector 122 and transceivers 124, 126, 132 may be incommunication with one another. Each transceiver 124, 126, 132 may be incommunication with a respective antenna, such as antenna 112, antenna114, and antenna 116. In other examples, fewer, additional, and/ordifferent components may be provided.

Electronic devices described herein, such as electronic device 102 andelectronic device 104 shown in FIG. 1 may be implemented using generallyany electronic device for which communication capability is desired. Forexample, electronic device 102 and/or electronic device 104 may beimplemented using a mobile phone, smartwatch, computer (e.g. server,laptop, tablet, desktop), or radio. In some examples, the electronicdevice 102 and/or electronic device 104 may be incorporated into and/orin communication with other apparatuses for which communicationcapability is desired, such as but not limited to, an automobile,airplane, helicopter, appliance, tag, camera, or other device.

While not explicitly shown in FIG. 1 , electronic device 102 and/orelectronic device 104 may include any of a variety of components in someexamples, including, but not limited to, memory, input/output devices,circuitry, processing units (e.g. processing elements and/orprocessors), or combinations thereof.

The electronic device 102 and the electronic device 104 may each includemultiple antennas. For example, the electronic device 102 and electronicdevice 104 may each have more than two antennas. Three antennas each areshown in FIG. 1 , but generally any number of antennas may be usedincluding 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 32, 64, or96 antennas. Other numbers of antennas may be used in other examples. Insome examples, the electronic device 102 and electronic device 104 mayhave a same number of antennas, as shown in FIG. 1 . In other examples,the electronic device 102 and electronic device 104 may have differentnumbers of antennas. Generally, systems described herein may includemultiple-input, multiple-output (“MIMO”) systems. MIMO systems generallyrefer to systems including one or more electronic devices which transmittransmissions using multiple antennas and one or more electronic deviceswhich receive transmissions using multiple antennas. In some examples,electronic devices may both transmit and receive transmissions usingmultiple antennas. Some example systems described herein may be “massiveMIMO” systems. Generally, massive MIMO systems refer to systemsemploying greater than a certain number (e.g. 96) antennas to transmitand/or receive transmissions. As the number of antennas increase, so togenerally does the complexity involved in accurately transmitting and/orreceiving transmissions.

Although two electronic devices (e.g. electronic device 102 andelectronic device 104) are shown in FIG. 1 , generally the system 100may include any number of electronic devices.

Electronic devices described herein may include receivers, transmitters,and/or transceivers. For example, the electronic device 102 of FIG. 1includes transceiver 120 and the electronic device 104 includestransceiver 124. Generally, receivers may be provided for receivingtransmissions from one or more connected antennas, transmitters may beprovided for transmitting transmissions from one or more connectedantennas, and transceivers may be provided for receiving andtransmitting transmissions from one or more connected antennas. Thetransmissions may be in accordance with any of a variety of protocols,including, but not limited to 5G signals, and/or a variety ofmodulation/demodulation schemes may be used, including, but not limitedto: orthogonal frequency division multiplexing (OFDM), filter bankmulti-carrier (FBMC), the generalized frequency division multiplexing(GFDM), universal filtered multi-carrier (UFMC) transmission, biorthogonal frequency division multiplexing (BFDM), sparse code multipleaccess (SCMA), non-orthogonal multiple access (NOMA), multi-user sharedaccess (MUSA) and faster-than-Nyquist (FTN) signaling withtime-frequency packing.. In some examples, the transmissions may besent, received, or both, in accordance with 5G protocols and/orstandards. Generally, multiple receivers, transmitters, and/ortransceivers may be provided in an electronic device - one incommunication with each of the antennas of the electronic device. Forexample, the transceiver 124 may be used to provide transmissions toand/or receive transmissions from antenna 112, while other transceiversmay be provided to provide transmissions to and/or receive transmissionsfrom antenna 114 and antenna 116.

Communication detectors described herein, may provide an indication tomultiple transceivers. So, for example, the electronic device 104 mayinclude three transceivers, including the transceiver 124, to serviceantenna 112, antenna 114, and antenna 116, respectively. Thecommunication detector 122 may be in communication with multiple (e.g.all) of the transceivers of the electronic device 104, and may providean indication of the presence or absence of a wireless communicationsignal in a portion of the wireless spectrum to the multiple (e.g. all)transceivers, including those coupled to the antenna 112, antenna 114,and antenna 116.

Examples of transmitters, receivers, and/or transceivers describedherein, such as the transceiver 120 and transceiver 124 may beimplemented using a variety of components, including, hardware,software, firmware, or combinations thereof. For example, transceiversmay include circuitry and/or one or more processing units (e.g.processors) and memory encoded with executable instructions for causingthe transceiver to perform one or more functions described herein (e.g.software).

It may be desirable in some examples to make more efficient use ofwireless spectra. For example, it may be desirable for one or moreelectronic devices described herein to determine that a particularportion of wireless spectra (e.g. one or more frequencies or frequencybands) currently contains a communication signal and/or is currentlyidle and/or available for use in providing and/or receiving atransmission. Particularly as wireless communications move toward 5Gstandards, efficient use of wireless spectra may become increasinglyimportant.

Accordingly, electronic devices described herein may include one or morecommunication detectors. For example, the electronic device 102 mayinclude communication detector 118 and the electronic device 104 mayinclude communication detector 122. Examples of communication detectorsdescribed herein may utilize properties of the MIMO system to determinewhether a particular portion of the wireless spectrum (e.g. one or morefrequencies or frequency bands) are in use. Communication detectorsdescribed herein may provide an indication to receiver(s),transmitter(s), and/or transceiver(s) that a particular portion of thewireless spectrum is idle and/or available for use. Responsive to suchan indication, a transmitter and/or transceiver may transmit and/orencode transmissions on or for the particular portion of the wirelessspectrum. Alternatively or additionally, an indication may be providedthat a wireless communication signal is present on a particular portionof the wireless spectrum. In some examples, the indication may berepresentative of encoded data in the wireless communication signal.Responsive to such an indication, a receiver and/or transceiver mayreceive and/or decode transmissions received on the particular portionof the wireless spectrum.

For example, the communication detector 122 may provide an indication tothe transceiver 124 that a particular portion of the wireless spectrumavailable at the antenna 112, antenna 114, and/or antenna 116 is idleand/or available for use. Responsive to the indication, the transceiver126 may prepare to encode and/or transmit transmissions using thatparticular portion of the wireless spectrum (e.g. on the particularportion of the wireless spectrum) for transmission via antenna 112.

In some examples, the communication detector 122 may provide anindication to the transceivers 126, 130, 132 that a particular portionof the wireless spectrum available at the antenna 112, antenna 114,and/or antenna 116 contains a communication signal. Responsive to theindication that a signal is included in the transmission, adecoder/precoder of the electronic device (e.g., decoder/precoder 320)may prepare to receive and/or decode transmissions using that particularportion of the wireless spectrum (e.g. on the particular portion of thewireless spectrum).

Examples of communication detectors described herein, including thecommunication detector 118 and/or communication detector 122 of FIG. 1may be implemented using hardware, software, firmware, or combinationsthereof. For example, the communication detector 118 and/orcommunication detector 122 may be implemented using circuitry and/or oneor more processing unit(s) (e.g. processors) and memory encoded withexecutable instructions for causing the communication detector toperform one or more functions described herein.

Examples of communication detectors described herein may advantageouslyutilize properties of the MIMO system in which they are located todetect whether a particular portion of the wireless spectrum is idleand/or available for use. For example, communication detectors describedherein may utilize a cross-correlation between multiple channels todetermine whether a particular portion of the wireless spectrum containsa wireless communication signal and/or is idle and/or available for use.In some example, communication detectors may utilize both across-correlation between multiple channels and an auto-correlationbetween the multiple channels (or different channels) to determinewhether a particular portion of the wireless spectrum contains acommunications signal and/or is idle and/or available for use. FIG. 2 isa schematic illustration of an example communication detector arrangedin accordance with examples described herein. The communication detector200 includes statistic calculator 202 and comparator 204. Receivedsymbols may be provided to the statistic calculator 202. The statisticcalculator 202 may calculate a statistic that may be provided tocomparator 204 for comparison with a threshold which may, e.g. retrievedfrom a memory and/or hard-coded into the comparator 204. The comparator204 may compare the statistic with a threshold and output an indicationof whether a wireless communication is present in the portion of thewireless spectrum and/or whether the portion of the wireless spectrum isidle and/or available for use. For example, a ‘1’ may be provided if theportion of the wireless spectrum includes a wireless communicationsignal. A ‘0’ may be provided if the portion of the wireless spectrum isidle and/or available for use. In other examples, a ‘1’ may be providedif the portion of the wireless spectrum is idle and/or available foruse, while a ‘0’ may be provided if the portion of the wireless spectrumincludes a wireless communication signal.

The communication detector 200 may be used to implement and/or beimplemented by any of the communication detectors described herein, suchas the communication detector 118 and/or the communication detector 122of FIG. 1 .

Examples of statistic calculators described herein, such as statisticcalculator 202 may receive information from two or more antennas (e.g.from a number of communication channels). Any number of antennas (andcorresponding inputs to the statistic calculator 202) may be used. Thestatistic calculator 202 is shown in FIG. 2 as receiving “M” inputs,labeled x_1(t), x_2(t) ... x_M(t). Accordingly, time-domain symbols maybe provided to the statistic calculator 202. Referring back to FIG. 1 ,for example, the communication detector 118 may receive symbolsindicative of RF energy in a portion of the wireless spectrum incidenton antenna 106, antenna 108, and/or antenna 110. A corresponding one ofthe transceivers 120, 124, 128 may process the symbols indicative of RFenergy in a portion of the wireless spectrum to generate time-domainsymbols indicative of 5G data. The communication detector 122 mayreceive the symbols processed by the transceivers for detection of an 5Gsignal.

Any portion of the wireless spectrum may be used. For example, theantennas may be tuned to a particular frequency and/or frequency band,and consequently the data provided by those antennas may relate to thatparticular frequency and/or frequency band. Examples of frequency bandsinclude those licensed by the FCC, and generally may include any RFfrequencies. Generally, RF frequencies may range from 3 Hz to 3000 GHzin some examples. In some examples, a particular band may be ofinterest. Examples of bands include all or portions of a very highfrequency (VHF) band (e.g. 30-300 Mhz), all or portions of an ultra highfrequency (UHF) band (e.g. 300-3000 MHz), and/or all or portions of asuper high frequency (SHF) band (e.g. 3-30 GHz). Example bands mayinclude 5G wireless frequency ranges, such as utilizing a carrierfrequency in the E band (e.g., 71 76 GHz and 81-86 GHz), a 28 GHzMillimeter Wave (mmWave) band, or a 60 GHz V band (e.g., implementing a802.11 ad protocol).

Example statistic calculators may calculate statistics based on RFenergy from a portion of a wireless spectrum of generally any width(e.g. 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or more MHz widths). If nosignal is found in the portion of the wireless spectrum by communicationdetectors described herein, then transceivers described herein maytransmit a signal in that portion of the wireless spectrum. If a signalis found in the portion of the wireless spectrum by communicationdetectors, that portion may not be used for transmission and/ordecoders/precoders described herein may be activated to receive and/ordecode the signal.

Example statistic calculators, such as the statistic calculator 202 maybe implemented in hardware, software, firmware, or combinations thereof.For example, statistic calculator 202 may be implemented wholly orpartially in circuitry, and/or by one or more processing units (e.g.processors) and memory encoded with executable instructions forstatistic calculation, which, when executed by the one or moreprocessing units, cause the statistic calculator to calculate statisticsdescribed herein.

The statistic calculator may calculate a cross-correlation between RFenergy received on multiple channels, an auto-correlation between RFenergy received on multiple channels, or combinations thereof. Thestatistic calculator 202 may provide a statistic to the comparator 204.

Examples of statistics provided by statistic calculators describedherein may include a cross-correlation of symbols indicative of RFenergy incident on multiple antennas in a particular portion of thewireless spectrum. The cross-correlation may be indicative of thepresence of a wireless communication signal. For example, consider acase H0 where only noise is incident on two antennas, and a case H1where a wireless communication signal that includes a signal withencoded data, is incident on two antennas. Mathematically, the null andalternate hypothesis can be represented as:

$\{ \begin{array}{l}{H0:x_{1}(t) = n_{1}(t),x_{2}(t) = n_{2}(t)} \\{H1:x_{1}(t) = n_{1}(t) + w_{1}(t)s(t),x_{2}(t) = n_{2}(t) + w_{2}(t)s(t),}\end{array} )$

where x₁ is the received time-domain signal corresponding to a noisesignal n₁ incident on the first antenna, and x₂ is the receivedtime-domain signal corresponding to a noise signal n₂ incident on thesecond antenna (e.g. the first antenna may correspond to antenna 106 ofFIG. 1 and the second antenna may correspond to antennal 108 of FIG. 1). A wireless communication signal is represented in case H1 by s(t). w₁and w₂ represent weights applied to the wireless communication signal bythe respective transceivers coupled to antennas 1 and 2, respectively.It can be expected that the portion of the wireless communication signalreceived at each of the antennas - antenna 1 and antenna 2 may be highlycorrelated (e.g., in a cross correlation operation). However, the noisesignals received at each antenna may be significantly less correlated.Mathematically, the cross-correlations of the symbols indicative ofreceived RF energy in each case - case H0 and case H1 can be expressedas:

$\{ \begin{array}{l}{H0:R_{12}( {t,0} ) = E\lbrack {x_{1}(t)x_{2}{}^{\ast}(t)} \rbrack = E\lbrack {n_{1}(t)n_{2}{}^{\ast}(t)} \rbrack = 0} \\{H1:R_{12}( {t,0} ) = E\lbrack {x_{1}(t)x_{2}{}^{\ast}(t)} \rbrack = w_{1}(t)w_{2}(t)E\lbrack {s(t)s^{\ast}(t)} \rbrack}\end{array} )$

where R₁₂ is the cross-correlation of symbols indicative of RF energyreceived at antenna 1 with the RF energy received at antenna 2. E[]represents the expected value of the expression in the brackets, and theasterisk indicates the transpose of the noted function. Note that in theH0 case, the cross-correlation is expected to have a zero (or near zero)value. In the H1 case (e.g. where a wireless communication signal thatincludes is present), the cross-correlation is expected to have asignificant amplitude (e.g. non-zero). Accordingly, thecross-correlation may provide a statistic for use in determining whethera wireless communication signal is present. Comparing a magnitude of thecross-correlation to a near-zero threshold value may allow for adetermination of whether a wireless signal is present in the portion ofthe wireless spectrum received.

In examples utilizing 5G wireless communication signals, the statisticincluding a cross-correlation may be calculated by the statisticcalculator 202 mathematically as follows:

$R( {t,0} ) = \frac{1}{U}{\sum\limits_{z = 0}^{U}{x_{1}( {t - z} )x_{2}^{\ast}}}( {t - z} )$

Where U may be the duration of a time period used to receive RF energyat an antenna. Accordingly, the statistic calculator 202 may multiplyenergy received at each of a plurality of times at the first antenna(represented as x (t-z) where t is the current time and z varies from 0to the total duration U) with the transpose of the same received at thesecond antenna. Those products may be summed over time units between 0and the total time duration U, which may be a 5G symbol duration. Thesum may be normalized by dividing by U in some examples.

In some examples, the statistic calculator 202 may utilize a recursivealgorithm to calculate a cross-correlation over multiple symbols, suchas 5G symbols. Such a recursive algorithm may be representedmathematically as:

$R( {t + 1,0} ) = \frac{1}{U + 1}R( {t,0} ) + \frac{U}{U + 1}x_{1}( {t + 1} )x_{2}^{\ast}( {t + 1} )$

So, for example, the statistic calculator may calculate across-correlation at a next time (e.g. t+1) by multiplying symbolsgenerated from the received RF energy at the first antenna at that timewith the transpose of the symbols generated from the received RF energyat the second antenna at that time. That product may be multiplied by aconstant relating to the symbol duration (e.g. U/U+1). That overallproduct may be added to the cross-correlation at the previous timemultiplied by a constant relating to the symbol duration (e.g. 1/U+1).

More generally, in some examples, the recursive algorithm may also berepresented as:

R(t + 1, 0) = αR(t, 0) + βx₁(t + 1)x₂^(*)(t + 1)

where 0 ≤ α, β ≤ 1 and α + β = 1.

In some examples, 5G wireless communication signals may include a guardinterval of length V (e.g., a cyclic prefix of the OFDM target signal).The guard interval of a 5G signal may be included N time periods fromthe start of the 5G signal, beginning at specific N time point in the 5Gsignal. The guard interval may include a cyclic prefix that repeats aportion of the signal at the N time point. For example, the beginning ofthe 5G signal may be repeated in the cyclic prefix. As such, a signalthat begins at time “z” and includes a cyclic prefix at time “N” mayhave the same data repeated at both time periods. When cross correlated,the beginning of the 5G signal and the guard interval including thecyclic prefix may be correlated. Accordingly, cross-correlations of thesymbols received at the beginning of an RF signal and symbols receivedat a guard interval time periods may be computed in accordance with:

$\begin{array}{l}{R( {t,0} ) = \frac{1}{U}{\sum\limits_{z = 0}^{U}{x_{1}( {t - z} )x_{2}^{*}( {t - z} ) + \frac{1}{V}{\sum\limits_{z = 0}^{V}{x_{1}( {t - z} )x_{2}^{*}( {t - N - z} ) +}}}}} \\{\frac{1}{V}{\sum\limits_{z = 0}^{V}x_{2}}( {t - z} )x_{1}^{*}( {t - N - z} )}\end{array}$

In such a case, the recursive algorithm may be represented, in Equation7, as:

$\begin{array}{l}{R( {t + 1,0} ) = \frac{1}{U + 1}R( {t,0} ) + \frac{U}{U + 1}x_{1}( {t + 1} )x_{2}^{*}( {t + 1} ) +} \\{\frac{1}{V}x_{1}( {t - z} )x_{2}^{*}( {t - N - z} ) + \frac{1}{V}x_{1}( {t - z} )x_{2}^{*}( {t - N - z} )}\end{array}$

Such a recursive algorithm may also be represented, in Equation 8, as:

$\begin{array}{l}{R( {t + 1,0} ) = aR( {t,0} ) + \beta x_{1}( {t + 1} )x_{2}^{*}( {t + 1} ) +} \\{\frac{1}{V}x_{1}( {t - z} )x_{2}^{*}( {t - N - z} ) + \frac{1}{V}x_{1}( {t - z} )x_{2}^{*}( {t = N - z} )}\end{array}$

where 0 ≤ α, β ≤ 1 and α + β = 1.

Accordingly, the statistic calculator may in some examples calculate across-correlation of symbols received at a guard interval incident on afirst antenna with symbols received at a guard interval incident on asecond antenna to provide a first cross correlation factor. Thestatistic calculator may further cross correlate a symbol duration U ofthe incident energy with a symbol duration U of the incident energy togenerate a second cross correlation factor. The statistic calculator maycombine, e.g. add, the two cross correlation factor to provide thestatistic to the comparator. For example, to achieve the computationexpressed in Equation 8, the statistic calculator may add the firstcross correlation factor and the second cross correlation factor togenerate the statistic provided to the comparator for comparison with athreshold.

While the example with respect to Equations 1-8 of statistic calculatorhave been described in the context of two antennas, it can beappreciated that cross correlation of multiple symbols indicative of RFenergy incident on respective antennas can be used to calculate astatistic, for example, when wireless communication signals are receivedby M respective antennas receiving M respective wireless channels. Forexample, consider a case H0 where only noise is incident on M antennas,and a case H1 where a wireless communication signal that includes asignal with encoded data, is incident on M antennas. Mathematically, thenull and alternate hypothesis can be represented as:

$\{ \begin{array}{ll}{H0:} & {x_{1}(t) = n_{1}(t);x_{2}(t) = n_{2}(t);\ldots\ldots\ldots\ldots;x_{M}(t) = n_{M}(t)} \\{H1:} & \begin{array}{l}{x_{1}(t) = n_{1}(t) + w_{1}(t)s(t);x_{2}(t) = n_{2}(t) +} \\{w_{2}(t)s(t);\ldots\ldots\ldots\ldots;x_{M}(t) = n_{m}(t) + w_{M}(t)s(t)}\end{array}\end{array} )$

H0 may represent the received data of each M wireless channel includingrespective noise signals. H1 may represent the received data of each Mwireless channel including respective noise signals and the targetsignal, s(t). The weights _(WM(t)) may represent respective weightsapplied to the target signal by the respective transceivers coupled tothe respective M antennas. It can be expected that the portion of thewireless communication signal received at each of the antennas at each Mantenna may be highly correlated (e.g., in a cross correlationoperation). However, the noise signals received at each M antenna may besignificantly less correlated. Mathematically, the cross-correlations ofthe symbols indicative of received RF energy in each case - case H0 andcase H1 can be expressed as::

$\{ \begin{array}{ll}{H0:} & {R_{ij}( {t,0} ) = E\lbrack {x_{i}(t)x_{j}{}^{*}(t)} \rbrack = E\lbrack {n_{i}(t)n_{j}{}^{*}(t)} \rbrack = 0} \\{H1:} & {R_{ij}( {t,0} ) = E\lbrack {x_{ij}(t)x_{ij}{}^{*}(t)} \rbrack = w_{i}(t)w_{j}(t)E\lbrack {s(t)s^{*}(t)} \rbrack}\end{array} )$

In Equation 15, i and j may be the index of each wireless channel (i,j,=1,2,...M) received at respective M antennas of the electronic device102. As noted above, E[] represents the expected value of the expressionin the brackets, and the asterisk indicates the transpose of the notedfunction. Note that in the H0 case, the cross-correlation is expected tohave a zero (or near zero) value. In the H1 case (e.g. where a wirelesscommunication signal that includes a signal with encoded data ispresent), the cross-correlation is expected to have a significantamplitude (e.g. non-zero). Accordingly, the cross-correlation mayprovide a statistic for use in determining whether a wirelesscommunication signal is present. Comparing a magnitude of thecross-correlation to a near-zero threshold value may allow for adetermination of whether a wireless signal is present in the portion ofthe wireless spectrum received. As can be appreciated by the disclosureherein, the inclusion of additional wireless channels (e.g., M wirelesschannels) may provide a more accurate or improved statistic, especiallywhen wireless communication signals are averaged over time to calculatethe statistic. For example, the multiple wireless channel involvementmay improve an SNR ratio of the statistic.

While the above example of 5G wireless communications signals have beendescribed in the context of two signals received from respective firstand second antennas, it can be appreciate that M RF signals may bereceived at respective M antennas. In the example, the statisticincluding a cross-correlation of M RF signals may be calculated by thestatistic calculator 202 mathematically as follows:

$R( {t,0} ) = \frac{1}{U}{\sum\limits_{i = 1}^{M}{\sum\limits_{j = i + 1}^{M}{\sum\limits_{z = 0}^{U}{x_{i}( {t - z} )x_{j}^{*}( {t - z} )}}}}$

U may be the duration of a time period to receive RF energy at Mantennas. Accordingly, the statistic calculator 202 may multiply thesymbols indicative of RF energy received at each of a plurality of timesat M antennas (represented as x (t-z) where t is the current time and zvaries from 0 to the total duration U) with the transpose of the samereceived at the M antenna. According to Equation 11, each symbolindicative of RF energy received at M antenna may be multiple with eachother symbol received at all the other M antennas. Those products may besummed over time units between 0 and the total time duration U, whichmay be a 5G symbol duration. The sum may be normalized by dividing by Uin some examples. Over the duration of several 5G symbols, a recursivealgorithm according to Equation 11 such that each 5G symbol is includedto calculate the statistic.

While the above examples with respect to statistic calculator 202 havebeen described with respect to cross correlation, it can be appreciatedthat other statistics may be calculated by other possibleimplementations of statistic calculators. While not depicted in FIG. 2 ,an additional statistic calculator may be added to the communicationdetector 200 such that the additional statistic calculator calculates astatistic for an additional comparator before the statistic calculator202 calculates a statistic for the comparator 204. Additional statisticcalculators may include a signal power autocorrelation statisticcalculator, a pilot signal statistic calculator that calculates thecross correlation of symbols indicative of a pilot signal received at aparticular antenna, or a guard interval statistic calculator thatcalculates the symbols generated from guard intervals solely. Forexample, a pilot signal statistic calculator may receive symbolsindicative of RF energy at antenna 106 and processed by thecorresponding wireless transceiver 120 to generate symbols for astatistic calculation that compares the symbols to the symbols of aknown pilot signal. Any such statistic calculators may be utilized aspart of a communication detector 200 that includes multiple statisticcalculators 202 and multiple comparators 204. From one perspective, anadditional statistic calculator and corresponding additional comparatorsbefore the statistic calculator 202 may be viewed as “soft” detection ora rough classification. The communication detector 200 may receive anadditional signal indicative of either (1) a wireless communicationsignal being present in the portion of the wireless spectrum (e.g. a‘1’); or (2) the portion of the wireless spectrum being idle and/oravailable for use (e.g. a ‘0’), and may thereafter transmit the signalindicative of the wireless communication signal being present or absentin the RF energy to a decoder/precoder (e.g., decoder/precoder 320) ofthe electronic device described herein.

The comparator 204 may be implemented in hardware, software, firmware,or combinations thereof. For example, the comparator 204 may beimplemented using circuitry for comparing values. In some examples, thecomparator 204 may be implemented using one or more processing units(e.g. processors) and memory encoded with executable instructions forcomparing with a threshold, which, when executed by the one or moreprocessing units, cause comparisons described herein to occur. Theprocessors and/or memory used by the comparator 204 may in some examplesbe wholly or partially shared with processors and/or memory used toimplement statistic calculator 202.

The communication detector 200 may be utilized as any of thecommunication detectors herein. For example, the communication detector118 or communication detector 122 may be implemented as thecommunication detector 200. As another example, the communicationdetector 320 may be implemented as the communication detector 200.

FIG. 3 is a schematic illustration of an electronic device 302 arrangedin accordance with examples described herein. The transceiver 320 may becoupled to antenna 308 and may have a receive path 304 and transmit path306. The receive path 304 may include an analog-to-digital converter(“ADC”) coupled to the antenna 308, followed by a digital down-converter(“DDC”), a cyclic prefix remover, a transform (e.g. a discrete Fouriertransform, or “DFT”), and an adding removal component. The transmit path306 may include an adding component, an inverse transform (e.g. aninverse Fourier transform), a digital up-converter (“DUC”), and adigital-to-analog converter coupled to the antenna 308. In the example,the adding component may add an additional processing field to data inthe transmit path 306, such as a guard interval period, apost-processing field, a sampling field, or a filtering field. Thetransceiver 320 may be used to implement and/or be implemented byexample transceivers described herein, such as the transceivers 120,124, 128 and/or the transceivers 126, 130, 132 of FIG. 1 . Transceiver324 may be coupled to antenna 310 and may have a receive path 314 andtransmit path 316. In some examples, additional, fewer, and/or differentcomponents may be included. Generally one transceiver may be providedfor each antenna used in an electronic device. Any M number oftransceivers may be included in the electronic device 302, with thetransceiver 324 being indicated as the Mth transceiver. In such cases,additional receive and transmit paths may be provided to thecommunication detector 318 and decoder/precoder 320.

A communication detector 318 may receive symbols indicative of RF energyfrom the transceivers 320, 324 via the respective receive paths 304,314. Components of the receive path 304 and/or transmit path 306 may beimplemented using circuitry (e.g. analog circuitry) and/or digitalbaseband circuitry in some examples. The communication detector 318 mayprovide a signal indication 330 to decoder/precoder 320. The signalindication 330 may be a signal that indicates the presence or absence ofa wireless communications signal including encoded data.

During operation, the transceiver 320 may be provided an indication thata portion of the wireless spectrum contains a wireless communicationsignal, e.g. from the communication detector 318. On receipt of anindication that a portion of the wireless spectrum contains a wirelesscommunication signal, the receive path 304 may operate to receive and/ordecode the wireless communication signal. In some examples, a decoderand/or precoder (e.g., a decoder/precoder) may be coupled to therespective receive paths 304, 314 and/or transmit paths 306, 316,respectively.

The digital down conversion operation in receive paths 304, 314 may downconvert the frequency domain symbols at a certain frequency band to abaseband processing range. In examples where 5G signals may be receivedby the transceiver 320, the time-domain 5G symbols may be mixed with alocal oscillator frequency to generate 5G symbols at a basebandfrequency range. Accordingly, the RF energy that may include time-domain5G symbols may be digitally down-converted to baseband. The addingremoval component in the receive paths 304, 314 may remove an addedprocessing field from the baseband data, such as a guard interval, fromthe frequency-domain 5G symbols. A DFT operation in the receive paths304, 314 may be implemented as an FFT operation that transforms thetime-domain 5G symbols into frequency-domain 5G symbols. For example,taking an example of an OFDM wireless protocol scheme, the FFT can beapplied as N-point FFT

$X_{n} = {\sum\limits_{k = 1}^{N}{x_{k}e^{{- t2\pi kn}/N}}}$

where X_(n) is the modulated symbol sent in the nth OFDM sub-carrier.Accordingly, the output of the FFT operation may form frequency-domainOFDM symbols. In some examples, the FFT may be replaced by poly-phasefiltering banks to output symbols for the synchronization operation.

The decoder/precoder may include various operations to process thereceive paths 304, 314. Generally, the decoder/precoder may process thereceive paths 304, 314 according to a decoding matrix that decodes themultiple symbols indicative of RF energy from each of the antennas 308,310. The decoder/precoder may precode data to be transmitted via theantennas 308, 310 along the transmit paths 306, 316.

The decoder/precoder may also include a channel estimator thatcompensates the symbols by some factor to minimize the effects of theestimated channel. A demodulation mapping operation may demodulate thedata outputted from the channel estimation operation. For example, aquadrature amplitude modulation (QAM) demodulator can map the data bychanging (e.g., modulating) the amplitude of the related carriers. Anymodulation mapping described herein can have a correspondingdemodulation mapping as performed by demodulation mapping operation. Insome examples, the demodulation mapping operation may detect the phaseof the carrier signal to facilitate the demodulation of the 5G symbols.The demodulation mapping operation may generate bit data from the 5Gsymbols to be further processed by a deinterleaver operation. Adeinterleaver operation may deinterleave the data bits, arranged asparity blocks from demodulation mapping into a bit stream for a decoderoperation, for example, the deinterleaver operation may perform aninverse operation to convolutional byte interleaving. The deinterleaveroperation may also use the channel estimation to compensate for channeleffects to the parity blocks. A decoder operation may decode the dataoutputted from the scrambler to code the data. For example, aReed-Solomon (RS) decoder ,turbo decoder, low-density parity-check(LDPC) decoder, or a polar decoder may be used as a decoder to generatea decoded bit stream for a descrambler operation. Such a decoder mayimplement a parallel concatenated decoding scheme. While described inthe context of a RS decoding and other such decoders, various decoderoperations are possible.

As described herein, the operations of the electronic device 302 caninclude a variety of RF processing operations performed with analogcircuits and/or digital implementations of analog circuits. Suchoperations can be implemented in a conventional wireless transceiver,with each operation implemented by specifically-designed hardware forthat respective operation. For example, a DSP processing unit may bespecifically-designed to implement the FFT operation. As can beappreciated, additional operations of a wireless transceiver may beincluded in a conventional wireless transceiver, and some operationsdescribed herein may not be implemented in a conventional wirelessreceiver. Accordingly, while specific components are not depicted inFIG. 3 that represent a corresponding specifically-designed hardwarecomponent of a transceiver 320, 324, it can be appreciated that thewireless receiver 110 may include such components and process thesymbols indicative of RF energy as described herein.

FIG. 4 is a flowchart of a method 400 in accordance with examplesdescribed herein. Example method 400 may be implemented using, forexample, system 100 in FIG. 1 , system 300 in FIG. 3 , or any system orcombination of the systems depicted in FIGS. 1-3 described herein. Theoperations described in blocks 404-432 may also be stored ascomputer-executable instructions in a computer-readable medium such as acomputer readable medium 115, 117 and/or computer readable medium 315,317.

Example method 400 may begin with a block 404 that starts execution ofthe a cross correlation routine. The method may include a block 408 thatrecites “receive, from each receiving unit or antenna, respective RFenergies.” As described herein, antennas 308, 310 may receive respectiveRF energies (e.g., RF signals at respective portions of the wirelessspectrum. In the example, the RF signals may be processed by therespective transceivers 320, 324. Block 408 may be followed by block 412that recites “for each respective receiving unit or antenna, crosscorrelate symbols indicative of a first RF energy with symbolsindicative of a second RF energy to calculate a statistic.” As describedherein, a statistic calculator may be configured to calculate astatistic including a cross-correlation of symbols indicative of radiofrequency (RF) energy received from at least two antennas. For example,a wireless communication signal may include an OFDM symbol and acorresponding cyclic prefix that is received during a guard interval ofthe OFDM symbol. The cross correlation may include a cross correlationfactor based on RF energy extracted from a guard interval time period.In an example including an additional statistic calculator, if theadditional statistic calculator corresponds to a signal powerautocorrelation statistic calculator, each respective receiving unit mayautocorrelate a respective power of the respective RF energies tocalculate a statistic to perform a “soft detection.” Block 412 may befollowed by block 416 that recites “retrieve at least one threshold froma memory.” For example, the comparator 204 may be used to compare astatistic calculated by the statistic calculator 202. In an example, thecomparator 204 may request the threshold from a memory database that ispart of an implementing computing device, from a memory database part ofan external computing device, or from a memory database implemented in acloud-computing device. In turn, the memory database may send thethreshold as requested by the comparator 204.

Block 416 may be followed by block 420 that recites “compare thestatistic to a corresponding threshold.” In the example, the statisticmay be compared to a threshold, indicating that symbols indicative ofthe first RF signal and the symbols indicative of the second RF signalcorrespond to encoded data. The encoded data may be encoded according toa modulation scheme associated with a 5G protocol. In the exampleincluding an additional statistic calculator, the statistic calculatedfrom the autocorrelation may compared to a corresponding threshold thatindicates the presence or the absence of the wireless communicationssignal including encoded data. Block 420 may be followed by a decisionblock 424 that recites “determine whether the statistic regarding thecross correlation passes a threshold.” In the example, the statistic maypass the threshold that is determined to indicate the presence orabsence of a wireless communications signal including encoded data. Ifthe statistic is determined to not pass the threshold that indicates thepresence of a wireless communication signal, the flow of method 400proceeds back to block 408 to receive further RF energy at the antennasor receiving units. If, however, the statistic is determined to pass thethreshold that indicates the presence of a wireless communicationsignal, the flow of method 400 proceeds to block 428 that recites“provide a signal indication representative of each RF energy includinga portion of the target signal.” In the example, the signal indicationmay indicate to an electronic device that the symbols indicative of RFenergy are to be decoded to recover a target signal, which is includedin the encoded data. In the example including an additional statisticcalculator, the signal indication may be provided to the communicationdetector that calculates the statistic regarding a cross correlation.Block 428 may be followed by block 432 that ends the example method 400.

In some examples, the block 416 may be an optional block. For example,during a 5G signal transmission, a threshold may be retrieved once(e.g., in a first cycle of a recursive algorithm) and then stored inlocal memory to be compare the sufficient statistic again at block 420.

The blocks included in the described example method 400 is forillustration purposes. In some embodiments, the blocks may be performedin a different order. In some other embodiments, various blocks may beeliminated. In still other embodiments, various blocks may be dividedinto additional blocks, supplemented with other blocks, or combinedtogether into fewer blocks. Other variations of these specific blocksare contemplated, including changes in the order of the blocks, changesin the content of the blocks being split or combined into other blocks,etc. Other additional blocks may be added such as “powering off adecoder responsive to receiving the signal indicative of the absence ofthe wireless communication signal,” “powering on a decoder responsive toreceiving the signal indicative of the presence of the wirelesscommunication signal,” and “decoding the symbols indicative of RF energyassociated with the first antenna according to a decoding matrix.”

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention.

What is claimed is:
 1. An apparatus comprising: a plurality of antennas;a transceiver configured to transmit, receive, or both, signals to,from, or both, at least a first antenna of the plurality of antennas; acommunication detector coupled to the transceiver and configured tocalculate a statistic including a cross-correlation of symbolsindicative of radio frequency (RF) energy received from at least two ofthe plurality of antennas including the first antenna in a particularportion of a wireless spectrum via the transceiver, the communicationdetector configured to provide a signal indicative of a presence orabsence of a wireless communication signal in the particular portion ofthe wireless spectrum based, at least in part, on a comparison of thestatistic with a threshold; and a decoder/precoder configured to receivethe signal indicative of the presence or absence of the wirelesscommunication signal, wherein the decoder/precoder is further configuredto power on into a power on state of the decoder/precoder responsive toreceiving the signal indicative of the presence of the wirelesscommunication signal, wherein the decoder/precoder is further configuredto power off into a power off state of the decoder/precoder responsiveto receiving the signal indicative of the absence of the wirelesscommunication signal, the communication detector configured toautocorrelate respective powers of the symbols indicative of RF energyreceived from the at least two of the plurality of antennas to calculatean additional statistic, the communication detector configured toprovide an additional signal indicative of an absence of the wirelesscommunication signal in the particular portion of the wireless spectrumbased, at least in part, on a comparison of the additional statisticwith an additional threshold, and wherein the decoder/precoder isfurther configured to power off into the power off state of thedecoder/precoder responsive to receiving the additional signalindicative of the absence of the wireless communication signal.
 2. Theapparatus of claim 1, wherein the statistic being below the threshold isindicative of the absence of the wireless communication signal, andwherein the statistic being above the threshold is indicative of thepresence of the wireless communication signal.
 3. The apparatus of claim1, wherein the communication detector is configured to autocorrelate therespective powers of the symbols indicative of RF energy received fromthe at least two of the plurality of antennas to calculate theadditional statistic to perform a soft detection of the presence ofabsence of the wireless communication signal.
 4. The apparatus of claim1, wherein the decoder/precoder comprises a channel estimator thatcompensates the symbols by a factor to reduce one or more channeleffects.
 5. The apparatus of claim 1, wherein the decoder/precoder isfurther configured to decode the wireless communication signal in theparticular portion of the wireless spectrum in accordance with adecoding matrix responsive to a signal indicative of the presence of thewireless communication signal.
 6. The apparatus of claim 1, furthercomprising: a second transceiver configured to transmit, receive, orboth, signals to, from, or both, at least a second antenna of theplurality of antennas, wherein the symbols indicative of radio frequency(RF) energy received from at least two of the plurality of antennasincludes symbols indicative of RF energy received from the secondantenna in another particular portion of the wireless spectrum via thesecond transceiver.
 7. The apparatus of claim 1, wherein thecommunication detector is implemented using one or more processing unitsand memory encoded with executable instructions for comparing with athreshold, which, when executed by the one or more processing units,cause comparisons of the cross correlation of the symbols to thethreshold.
 8. An apparatus comprising: a plurality of antennas; a firsttransceiver configured to receive a first radio frequency (RF) signalfrom a first antenna of the plurality of antennas; a second transceiverconfigured to receive a second radio frequency (RF) signal from a secondantenna of the plurality of antennas; a first communication detectorcoupled to the first transceiver and the second transceiver, the firstcommunication detector configured to cross correlate symbols indicativeof the first RF signal and symbols indicative of the second RF signal tocalculate a first statistic including a cross-correlation of symbolsindicative of the first RF signal and symbols indicative of the secondRF signal, wherein the first communication detector is furtherconfigured to provide a first signal indicative of a presence or absenceof encoded data in the first RF signal or the second RF signal based, atleast in part, on a comparison of the first statistic with the firstthreshold; a second communication detector coupled to the firsttransceiver and the second transceiver, the second communicationdetector configured to auto-correlate respective powers of the first andsecond RF signals to calculate a second statistic, wherein the secondcommunication detector is further configured to provide a second signalindicative of a presence or absence of encoded data in the first RFsignal or second RF signal based, at least in part, on a comparison ofthe second statistic with a second threshold; and a decoder/precodercoupled to the first communication detector and configured to receivethe first signal indicative of the presence or absence of the encodeddata in the first RF signal or the second RF signal, wherein thedecoder/precoder is further configured to power on responsive toreceiving the first signal indicative of the presence of the encodeddata in the first RF signal or the second RF signal, wherein thedecoder/precoder is further coupled to the second communication detectorand configured to receive the second signal indicative of a presence orabsence of encoded data in the first RF signal or second RF signal, andwherein the decoder/precoder is further configured to power offresponsive to receiving the second signal indicative of the absence ofthe encoded data in the first RF signal or the second RF signal.
 9. Theapparatus of claim 8, wherein the statistic being below the threshold isindicative of the absence of the wireless communication signal, andwherein the statistic being above the threshold is indicative of thepresence of the wireless communication signal.
 10. The apparatus ofclaim 8, wherein the first or second communication detector isconfigured to auto-correlate the respective powers of the symbolsindicative of RF energy received from the at least two of the pluralityof antennas to calculate the additional statistic to perform a softdetection of the presence of absence of the wireless communicationsignal.
 11. The apparatus of claim 8, wherein the first statisticcomprises a first cross correlation factor including the symbolsindicative of the first RF signal and the symbols indicative of thesecond RF signal and a second cross correlation factor including symbolsindicative of a first guard interval time period associated with thefirst RF signal and symbols indicative of second guard interval timeperiod associated with the second RF signal.
 12. The apparatus of claim8, wherein the first communication detector is configured to calculate across correlation of the symbols indicative of the first RF signal orthe symbols indicative of the second RF signal with a pilot signal or aguard interval statistic calculator configured to calculate the symbolsindicative of a first guard interval time period associated with thefirst RF signal and symbols indicative of second guard interval timeperiod associated with the second RF signal, and wherein the secondcommunication detector is configured to calculate an autocorrelation ofthe first RF signal or the second RF signal.
 13. The apparatus of claim8, wherein the first transceiver comprises: an analog-to-digital (ADC)converter configured to convert the RF energy to a digital symbols; adigital down converter (DDC) configured to mix the digital symbols usinga carrier signal to generate down converted symbols; and a fast Fouriertransform (FFT) configured to convert the down converted symbols domainto generate the symbols indicative of RF energy.
 14. The apparatus ofclaim 13, wherein the RF energy includes time-domain 5G symbols that aremixed by the DDC with a local oscillator frequency to generate 5Gsymbols at a baseband frequency range.
 15. A method, comprising:receiving, from each antenna of a plurality of antennas, respective RFenergies, each antenna coupled to a respective receiving unit of aplurality of receiving units; for each respective receiving unit,autocorrelating a respective power of the respective RF energies tocalculate a first statistic; comparing, at a communication detector, thefirst statistic to a first threshold that indicates a presence or anabsence of a wireless communications signal including encoded data;providing a first signal indication based on a determination that thefirst statistic passes the first threshold, the first signal indicationrepresentative of the presence of the wireless communications signalincluding the encoded data; based on obtaining the first signalindication, for each respective receiving unit, cross correlatingsymbols indicative of RF energy associated with a first antenna with atleast other symbols indicative of RF energy associated with at least asecond antenna to calculate a second statistic; comparing, at a secondcommunication detector, the second statistic to a second threshold thatindicates the presence or the absence of the wireless communicationssignal including encoded data; determining that the second statisticdoes not pass the second threshold; providing a second signal indicationrepresentative of the absence of a wireless communications signalincluding encoded data; and powering off a decoder responsive toreceiving the second signal indicative of the absence of the wirelesscommunication signal.
 16. The method of claim 15, wherein the statisticbeing below the threshold is indicative of the absence of the wirelesscommunication signal, and wherein the statistic being above thethreshold is indicative of the presence of the wireless communicationsignal.
 17. The method of claim 15, further comprising: compensating thesymbols by a factor to reduce one or more channel effects of anestimated channel; and demodulating data outputted from the channelestimation operation based at least in part on detecting the phase ofthe carrier signal.
 18. The method of claim 15, wherein crosscorrelating symbols indicative of the respective RF energies comprisesutilizing a recursive method to calculate a cross correlation over thesymbols and the at least other symbols, the cross correlation of thesymbols corresponding to the second statistic.
 19. The method of claim18, wherein utilizing the recursive method to calculate the crosscorrelation over the symbols comprises: transposing the at least othersymbols indicative of RF energy associated with the second antenna;multiplying the transposed at least other symbols with the symbolsindicative of RF energy associated with the first antenna to generate anintermediate result; and multiplying the intermediate result with aconstant associated with a symbol duration of the symbols indicative ofRF energy associated with the first antenna.
 20. The method of claim 18,wherein utilizing the recursive method to calculate the crosscorrelation over the symbols comprises: multiplying transposed at leastother symbols of each respective RF energy with the symbols indicativeof RF energy associated with the first antenna to generate a pluralityof intermediate results and intermediate result; and generating thefirst statistic based on summations of the intermediate results based ona duration of a time period to receive the respective RF energies and anumber of antennas of the plurality of antennas.